Especially in the automotive industry, there is a trend toward using more non-metallic materials, e.g., thermoplastic or thermoset materials. In automobiles, these materials are often used for forming body panels which are bonded to metal frames or metal unibodies. Adhesives are used to bond the non-metallic body panels to the metallic frames or unibodies. Currently, a method using plastic "mill and drill pads" is used to secure the metallic and non-metallic parts together long enough for adhesive between them to fully cure. In this method, plastic pads on the body panel are milled to fit the metal frame and drilled for insertion of a screw which secures the metal frame and the body panel together until full cure of the adhesive is accomplished. Usually, full cure of the adhesive occurs when the body panels are passed through dry-off or paint-curing ovens.
However, the currently used mill-and-drill-pad method is labor and time intensive and, therefore, expensive for the auto manufacturer and, finally, for the consumer.
It is, therefore, desirable to be able to eliminate the need for the mill-and-drill-pad procedure. One such way would be to accelerate the cure of the adhesive so that it is at least partially cured and has enough strength to keep the metallic and non-metallic parts together until they reach the paint-curing ovens.
During automobile production, body panels are attached to the frame and the frame quickly becomes enclosed, making it difficult to maneuver equipment inside the frame. Therefore, it would also be desirable to accomplish the adhesive cure acceleration by approaching the substrate from the outside only.
It is, therefore, an object of the present invention to provide an apparatus for easily and inexpensively heating a substrate having an electrically-conductive portion and a non-electrically-conductive portion.
It is another object of the present invention to provide an apparatus which accelerates the curing of an adhesive between an electrically-conductive material and a non-electrically-conductive material without damaging the adhesive or the electrically-conductive or non-electrically-conductive materials.
It is another object of the present invention to provide an apparatus which accelerates the curing of an adhesive between a steel space frame and a plastic automotive body panel so that mill and drill pads are unnecessary.
It is yet another object of the present invention to provide an apparatus which would efficiently heat a substrate using access from only one side of the substrate.